The work camps in Nazi Germany had the explicit goal, discussed in letters of the people running them, of bringing the interned to their "natural end", i.e. work them to death, and many people were indeed killed this way.
apparently that was already a German phrase the Nazi's just thought it would be funny to write it on a camp where they work people to death. The slogan is a stupid joke. Because that's their sense of humour
fundamental to understanding nazis is to fully appreciate that they just suck.